NAEP Technical DocumentationStratification by Achievement Data and Median Income for the 2009 State Assessment

			Jurisdictions Using Achievement Data or Median Household Income in Stratification

The achievement data are derived from the results of state assessment programs that were obtained from each jurisdiction. The contents of the achievement data files varied by jurisdiction and included achievement measures for a variety of subjects, grades, and multiple assessment programs. One achievement measure was selected for each responding jurisdiction to be used in the stratification process. Where available, the achievement data were used for implicit stratification by grade. Since the achievement data are more current than the median household income data, as well as more likely to be well-correlated to NAEP assessment scores, they were judged to be a more effective stratification variable. The achievement measures were selected according to the following criteria:

• Achievement measures from state assessments conducted in mathematics and reading (in that order of priority) were utilized, if available. For grade 4, data from fourth-grade assessments were used, if available; otherwise, data from third-grade assessments. For grade 8, data from eighth-grade assessments were used, if available; otherwise, data from seventh-grade assessments. For both grades, data from 2005 assessments (the latest available) were preferred; 2004 assessments were used as secondary choices. For grade 12, achievement measures were not available. 

• Achievement measures should match to at least 70 percent of the schools on the sampling frames.

• Achievement measures should differentiate schools from one another. For example, district-level measures, those with high missing rates or pass/fail indicators, were judged not to be useful for differentiating schools. In addition, achievement measures that did not have good dispersion were not used for stratification.

• All other things being equal, the possibilities for score types were average scale score, median scale score, percentile rank, median percentile rank, normal curve equivalent, raw score, index score, and percentage above a particular cut score or quartile. In general, the availability varied for any given state/grade/subject/year.

Achievement data useful for implicit stratification were obtained from 48 of 51 jurisdictions for the fourth-grade assessment, and 42 of 51 jurisdictions for the eighth grade assessment. Where achievement data were not used, median household income from the 2000 Census was used.

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